Method of forming metallic sheet members



Dec. 14, 1965 R. E. ROPER METHOD OF FORMING METALLIC SHEET MEMBERS Filed Feb. 23, 1962 5 Sheets-Sheet 1 KM, 10ml), SM Mu'lmt Dec. 14, 1965 R. E. ROPER 3,

METHOD OF FORMING METALLIC SHEET MEMBERS Filed Feb. 23, 1962 5 Sheets-Sheet 2 INVENTOR. RALPH E. RoPER KM wmwsm mm AH'o vn ays METHOD OF FORMING METALLIC SHEET MEMBERS Filed Feb. 23, 1962 Sheets-Sheet "iii n r L l a 1% 6 J qs 10 as l2 I W F. 5

7 8a Ho 37 1g. 0

1o I as 1 INVENTOR. .3 23 RALPH E. Room I I H g 1| XMMMsmMwu-m L.-@ 68 H l0 AH'orvleys Dec. 14, 1965 R. E. ROPER 3,222,910

METHOD OF FORMING METALLIC SHEET MEMBERS Filed Feb. 23 1962 5 Sheets-Sheet 4 Fig. 7. INVENTOR.

RALPH E. ROPER 96M, ZUwdmJ, Smith wzlkud AHovneys Dec. 14, 1965 R. E. ROPER 3,222,910

METHOD OF FORMING METALLIC SHEET MEMBERS Filed Feb. 25, 1962 5 Sheets-Sheet 5 Fig. 8.

INVENTOR. RALPH E. RoPER WZ/WSM $211M United States Patent 3,222,910 METHOD OF FORMINGMETALLIC SHEET MEMBERS Ralph E. Roper, Indianapolis, Ind.', assignorto Wallace lixpandingMachines, Inc., Indianapolis, Ind., a corporation of Indiana Filed Feb. 23,- 1962, Ser. No. 175,152 7 Claims. (Cl; 72-332) The present invention-relates to a method for forming metallic sheet into parts such as automobile fenders, doors,- bonnets and;other' drawn sheet metal parts.

It is conventional practice in the. automobile industry to draw fenders, doors andinfact practically all sheet metal parts of this type by the. use of toggle presses. These.- toggle; presses usually operate to grip a fiat sheet of metal around andadjacent the. edge thereof. The sheet is then formed inwardly of the gripped edge thereof byutheause of cooperating. male and-female dies. Many problems aretinvolved in drawing metal in this manner. First, it "is frequently necessary to 'overdraw a part in order that' ithave the. correct final shape. The amount 0f*overdrawing' necessary canonly be an educated guess which must be made by one having long experience in the'field. Even then the final product is unpredictable and may be far outside the desired tolerances.

Second, the. toggle press is usually the weaklink in the formingprocess. In practically all production lines, the various other apparatus such as trimming and flanging devices and the like must waiton the toggle press which paces the a production line. Also, the toggle press is usuallycapable of forming only a single shape or part at one time and consequently, long expensive down time is experienced during which the toggle press is converted overfrom one part to another. For example, the toggle press might be operated to produce left-hand automobile doors for a period of time. and then. converted over to right-hand automobile door-s. It will be evident that this situation also results in storage problems of the one type of part which has been mostrecently formed and also causes difiiculties in production planning.

Consequently, a primary object of thepresent invention is .to provide an improved method for forming metallic sheet material into parts.

A further object of the present invention is to provide a method for sheet metal forming which, as compared to toggle presses, drastically reduces scrap, greatly increases structural strength, permits the-use of lighter gauge metal and reduces tooling costs,

Another object of the present invention is to provide a method for sheet metal forming which, as compared to toggle presses, drastically reduces initial cost.

Still another object of the invention is to provide a method for sheet metal'forming which, as compared to toggle presses, increases speed of production, reduces the amount of metal finishing required and makes possible greater flexibility in the shapes that can be formed.

Related advantages ofthe invention are that it makes possible precise forming of 'parts without guesswork and makes possible the forming of'a plurality of parts simultaneously, thus reducing storage space necessary and also reducing loss of production time in tooling change-over.

Related objects and advantages will become apparent as the description proceeds.

One embodiment of the method of the present invention comprises the steps of bending a sheet of'metal into a closed shape with the opposite edges thereof in engagement, securing the opposite edges together, expandingand stretching the closed shape over a die structure having a discontinuous forming face wherein each continuous portion of the forming face defines one complete surface of a respectiveone of said parts and cutting the metal between the thus formed partsto separate them.

One embodiment-of the apparatus of the present inventlon comprises a. plurality of dies each havingan outwardly facing surface which has the shape desired for one complete surface of arespective one of the parts, means for simultaneously moving the dies radially out-wardly to stretch an annular sheet-metal member thereover'and to form the parts, and means for separating the thus formed parts.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims.-

FIG. 1 is atop plan viewof an expander forming a part of the present invention.

FIG. 2 is a perspective view of a-closed sheet metal member preformed for reception within the expander of FIG. 1.

FIG. 3 is avert-ical section .taken along the line 33 of FIG. 1 in the direction of the arrows.

FIG. 4 is a top plan view similarto FIG; 1 but showing apparatus forming a part of the presentinventionzand taken generally along the line 8-8 of FIG. 6.

FIG. 9 is a fragmentary horizontal section taken along y the line 99 ofFIG. 8 in the direction of the arrows :but showing the device in a diflferentoperating position.

Referring now more particularly to the drawings, there is illustrated in detail in FIGS 1, 3, 4 and :5 an expander apparatus 9 which operates upon the rectangularshaped closed sheet metal structure shown in FIG. 2. to expand it into a cluster of connected sheet metal parts.. The expander includes 'abase 10.which is supportedupon vertically extending members 11 and hasfixed'thereto a cylindrical or ring-shaped member 12.; In order" to firmly fix the ring-shaped member to the base, the member 12 is provided with a downwardlyprojectingannular lip 15 which is receivedwithin a suitable annular recess 16 in the base. An annular top plate 17 is fixed-to-the upper edge of the ring-shaped member 12 in similarfasha ion with lip '18 in recess 19-whereby a rigid cylindrical housing 20 is provided. To provide an even further amount of strength and rigidity, four shouldered vertical pins 21 are received within suitable apertures in the base and top plate and fix these members in spaced relation.

A'plurality of radially extending keys 221 are fixed to and received within suitable radially extending apertures.

in the base 10. The keys 22 provide trackwlays for four tool or die carrier members 25 and 26. Fixed to the outer faces of the carriers 25- and 26 are scab dies .27

and 28 which can be removed and replaced by different shaped dies if desired depending upon the type of part being formed. The diesand die carriers 25-28 are movable between the base 10 and a center cluster top plate 30 which is fixed in spaced relation to the base 10 by means of shouldered bolts'31; the. top plate 30 acting to retain the di'ecarriers uponthe trackway formingkeys 22';

Each of the die-carriers25 and-26'has a tapered inner surface 32 'and 33 \against which-the tapered outer surfaces 35 and 36 of 'aninner driver member 37 act. The driver member 37 is fixed to a vertically extending piston rod 40 of a fluid motor-41-which is'fixed-to the base 1G.

Patented Dec. 14,- 1965.

When the motor 41 is operated to move the driver 37 downwardly, the surfaces 35 and 36 of the member cam against the inner surfaces 32 and 33 of the die carriers to move them outwardly. When the fluid motor 41 is operated to move the piston rod 40 and driver member 37 upwardly, the die carriers 25 and 26 are drawn inwardly by means of T-shaped keys 42 and 43 (FIG. 3) fixed to the surfaces 35 and 36 and received within T- slraped slots 45 and 46 (FIG. 4) formed within the die carriers. Thus, it can be appreciated that vertical movement of the driver member 37 in opposite directions produces inward and outward movement of the die carriers 25 and 26 and the dies 27 and 28 mounted thereon.

The surfaces 32 are tapered at a different and greater angle to the vertical than the surfaces 33. Thus, when the driver member 37 is moved to its uppermost position as shown in FIGS. 1 and 3, the dies 27 are moved a greater amount radially inwardly than are the dies 28. Each of the dies 28 is formed with a recess 47 in its rearward face which receives the end portion 50 of each of the dies 27. When the dies 27 and 28 are moved to their outward position by the driver member 37, the dies 27 travel a greater radial distance than do the dies 28. By the above described arrangement, the circumference of the inner dies, when in their innermost position, can be made smaller without reducing the distance (taken horizontally) across the forming faces 51 and 52 of those dies.

Four outer die carriers 55 are radially slidable along the trackway-providing keys 22. Preferably, bearings 23 formed of bronze material or the like, are provided in the base at its upper surface across which the die carriers 55 and 26 and 27 travel. Each of the die carriers 55 has an outer die 56 mounted thereon. The outer dies 56 are provided with inwardly projecting portions 57 which function to form the indentations and recesses in the external surfaces of the cluster of parts being formed in the work piece '60.

The annular top plate 17 has fixed in the lower face thereof radially-extending keys 61 which project into upwardly-opening grooves 62 in the upper surface of the outer die carriers 55 and act as additional trackways for the die carriers 55. The outer die carriers are moved inwardly and outwardly by means of cam means 65 which may be in the form of a ring. The cam ring 65 is provided with tapered inwardly facing cam surfaces 66 which act against cooperating surfaces 67 on the external faces of the outer die carriers 55. A plurality of fluid cylinders 68 are fixed to the base 10 and have their piston rods 69 fixed to the cam ring 65 whereby upward projection of the piston rods causes the cam surfaces 66 to move across the surfaces 67 of the outer die carriers and to move the outer die carriers radially inwardly. The innermost position of the die carriers 55 is shown in FIG. 5. In this position, the vertical surfaces 70 of the cam ring 65 are in engagement with the vertical surfaces 71 of the outer die carriers. Consequently, further vertical movement and seating of the cam ring 65 against the top plate 17 produces no corresponding radial movement of the die carriers and the die carriers are locked in the illustrated inward position by the surfaces 70 and 71.

Each of the forming faces 51 and 52 of the dies 27 and 28 defines the desired shape of the complete inner surface of a respective one of the parts to be formed from the work piece 60. In the illustrated embodiment, four automobile door panels are to be formed from the closed sheet metal work piece 60. Referring to FIG. 4, these four desired shapes are shown at 75, 76, 77 and 78 an are connected by scrap metal portions 79.

In order to form the cluster of parts shown in FIG. 4, the rectangular work piece 60 is placed about the dies 27 and 28 in the position shown in FIG. 1 with the dies all drawn to their innermost position by projection of the piston 40 and driver member 37 to their uppermost position as shown in FIG. 3. The outer cam ring 65 is then moved from the position of FIG. 3 to the position of FIG. 5 by projection of the piston rods 69 of 'the cylinders 68. The driver member 37 is then moved downwardly to the position of FIG. 5 causing the dies 27 and 28 to move outwardly and to stretch the metal of the work piece 60 thereover. Because of the fact that there are no binders or devices gripping any of the metal of the Work piece, it is free to flow uniformly and to stretch out not only over the forming faces of the dies 27 and 28 but also at the scrap portions 79 whereby the final transverse dimension taken horizontally across the parts 75-78 is greater than the complete initial circumference of the work piece 60 as shown in FIG. 2. It should be mentioned that the horizontal cross section of the final parts 75-78 is not necessarily constant and in most cases (for example, in forming fenders) varies greatly from the top of the parts to the bottom thereof. Thus, the metal flows and stretches not only horizontally but also vertically.

As the dies 27 and 28 move outwardly, they engage the outer dies 56 and cause the projections 57 of the outer dies to force against the work piece 60 and to produce the desired indentations and recesses in the external surface of the parts 75-78. The final forming position of the apparatus is shown in FIG. 4. It can be appreciated that until the inner and outer dies are fully engaged, the metal is free to flow and stretch and there are no binders or members gripping the work piece and preventing free flow.

The outer dies are then moved outwardly to their original position by downward movement of the cam ring 65. The cam ring has mounted thereon a plurality of T-shaped keys 80 which are receivable within T-shaped slots 81 in the external surface of the die carriers 55. As the cam ring moves downwardly, the keys 80 move into the slots 81 and cam against the surfaces 82 of the outer dies causing the outer dies to be moved outwardly away from the work piece and to return to the position shown in FIGS. 1 and 3. The driver member 37 is raised upwardly by projection of the piston rod 40 causing the die carriers 25 and 26 and the dies 27 and 28 to be moved inwardly and to return to the position illustrated in FIGS. 1 and 3.

It should be noted that the parts 75 and 77 are allochirally related to the parts 76 and 78. In the illustrated embodiment of the invention, the parts 75 and 77 may be identical left-hand automobile doors and the parts 76 and 78 identical right-hand automobile doors. Because such allochirally related parts have the same vertical dimension and similar shapes, the present invention is particularly adapted for forming such parts. This is true because the amount of metal needed and the amount of drawing needed for each such part around the work piece is equal. Thus, an inexpensive and easily constructed work piece of constant axial length is used in the present embodiment.

Fixed to the base 10 is a plurality of fluid cylinders 85 having piston rods 86 with pads 87 on the distal ends thereof. The fluid motors 85 are then operated to project their piston rods and raise the feet 87 to lift the formed work piece upwardly out of the apparatus. The work piece is then picked up by automatic transfer means and carried to further apparatus which cuts the work piece along the scrap portion area 79 to separate the parts. This further cutting apparatus is described in detail below.

Referring to FIG. 6, the complete system for practicing the method of the present invention is illustrated schematically. A conventional barrel forming and welding machine 90 functions to convert strips of sheet metal into sheet metal cylinders of a desired diameter. The machine 90 bends the sheet metal until the opposite edges thereof engage and then welds the opposite edges together toform the desired cylindrical shape. A suitable machine of this type for use in the present invention is Special Appliance Type barrel welder manufactured by Federal-Warco Division of McKay Machine 00., Warren, Ohio. Alternatively, this welded cylindrical work piece could be manufactured manually by manually bending a rectangular sheet of metal until the opposite edges engage, welding the edges together and grinding down the weld in a conventional manner so that the thickness of the welded portion is equal to the thickness of the sheet metal.

After the machine has formed the sheet metal into the desired welded cylindrical work piece, the cylindrical Work piece is moved by the machine 90 onto an expander 91 forming a part of preforming apparatus 92. As shown in dotted lines in FIG. 7, the expander 91 may be tilted to a position wherein the axis of the expander 91 extends horizontally so that the cylindrical work piece can be placed thereover by machine 90.

The preformer 92 includes a base 95 including vertical post 96 and horizontal members 97 fixed to and connecting the posts 96. A table 100 is pivoted upon the base 95 at 101. Four dies 102 are horizontally slidable upon the upper surface of the table 100 and are guided for radial movement by guide members 103. Each of the dies 102 is provided with a pair of the guide members 103, each of which is fixed to the table 100 and has an inwardly projecting portion 105 received within a horizontal groove in the die 102. It can be seen that the guide members 103 permit only horizontal radial movement of the dies 102. A driver member 106 having a cross-shaped cross section is received within the dies 102 and is keyed thereto by T-shaped keys 107 in the manner described above with respect to the expander of FIGS. 1, and 3-5. Similarly to the above described expander, the driver 106 and dies have cooperating tapering cam surfaces 108 and 109. Thus, vertical movement of the driver 106 in opposite di rections produces inward and outward movement of the dies 102. Axial movement of the driver member 106 is effected by clinder motor 110 fixed to the table 100 and having its piston 111 fixed to the driver member.

A tilt cylinder motor 112 is pivoted to the horizontal members 97 and has its piston rod 115 pivoted to the table 100. The tilt cylinder 112 functions to move the table 100 between the solid line position and the dotted line position of FIG. 7. As mentioned, when the expander 91 is in the dotted line position, the cylindrical work piece is received thereon from the machine 90, the expander 92 is then moved to the solid line position wherein the cylinder seats itself against the table 100. The cylinder 110 is then operated to move the driver member 106 downwardly and to expand the dies 102 preforming the cylindrical work piece into the rectangular Work piece shape 60 shown in FIG. 2. The work piece is then removed from the expander 91 by returning the driver 106 of the expander to the upward illustrated solid line position and by suitable automatic transfer apparatus 115. This automatic transfer apparatus functions to transport the work piece 60 to and into the expander 9 of FIGS. 1 and 35 where the above described forming operations take place. As an alternative to the above described barrel forming machine 90 and preformer 92, the rectangular work piece of FIG. 2 might be formed and welded by a single machine. This alternative is especially desirable where the work piece is relatively large.

The rectangular work piece is then expanded to the shape shown in FIG. 4 by means of the expander apparatus 9 and as above described in connection with FIGS. 1 and 3-5. The expanded work piece is then lifted out of the expander 9 by means of the fluid cylinders 85 and is transported by automatic transfer apparatus 116 to a splitter apparatus 117 shown schematically in FIG. 6 and in greater detail in FIGS. 8 and 9. The function of the splitter apparatus 117 is to separate the various parts formed in the expanded work piece from one an other. In the present embodiment, the splitter apparatus separates the parts 7578 by a single cut through each of the scrap portions 79. The four resulting parts are then conveyed along conventional conveyors 120 to suitable conventional trimmer die apparatus which function to trim the remaining portions of the scrap 79 from the individual parts 75-78. Alternatively, the splitter apparatus 117 may be designed so as to complete this trimming function in a single operation.

Referring more particularly to FIGS. 8 and 9, the splitter apparatus comprises vertical supporting structure having a cross shaped base plate 126 fixed to the upper ends thereof. Four cutter assembly support plates 127 are slidably mounted for horizontal radial movement with relation to the axis of the splitter apparatus by means of L-shaped cross section guide members 130 fixed to the base 126. Each of the guides 130 has an inwardly projecting portion 131 which extends over its respective support plate 127 and retains the support plate between the guides 130.

A threaded adjusting rod 132 is provided for radially adjusting the position of each support plate 127 and is rotatably mounted at one end upon the vertical supporting structure 125 and at the other end upon the base 126 by means of suitable bearing elements 135 and 136 fixed to the structure 125 and the base 126, respectively. The bearing elements 135 and 136 include suitable means for retaining the rod 132 against axial movement. At the outward end of each rod 132, there is fixed a crank 137 for rotating the rod. Each of the support plates 127 has a depending element 140 fixed thereto and threadedly receiving the rod 132. It can be appreciated that the support plate 127 may be adjusted as to radial position by rotating the rod 132 by means of the crank 137. Normally, the support plate 127 will be adjusted for a particular type of part and will remain in the adjusted position until manufacture of that type of part has been completed at which time the tooling of the splitter apparatus as well as the positions of the support plates 127 are converted over to a new part.

A cutter assembly 140 is mounted for radial horizontal movement upon each of the support plates 127 by means of L-shaped cross-section guides 141 fixed to the support plates 127 and extending over the base plate 143 of each cutter assembly.

A fluid motor 142 is fixed to each support plate 127 and has its piston rod 145 fixed to the base 143 of the cutter assembly 140. Anvil structure 146 is fixed to each of the cutter assembly base plates 143 and extends upwardly therefrom. The anvil structure includes a die carrier 147 and an anvil die 150 fixed to the outer surface of the die carrier 147. Each anvil die 150 has an outwardly facing die face 151 shaped identically to that portion of the inner surface 152 of the Work piece 155 which is adjacent to the area to be cut. In the center of each anvil die 151, there is an indentation 156 which extends the complete length of the die and has a shape corresponding to the cutter die 157. Because the anvil die face 151 is shaped identically to the work piece, the anvil die structure 146 is used to position the work piece prior to the cutting operation. This positioning function is accomplished by actuating the fluid cylinders 142 to retract their piston rods 145 and move the cutter assemblies 140 radially outwardly causing the anvil faces 151 to engage the work piece at the areas 152 and position the Work piece for the cutting operation.

Each of the cutter assemblies further includes vertical side plates 160 and a rear or outer vertical plate 161 all of which are fixed to the base plate 143 of the assembly and define a three-sided enclosure for the cutter die structure 162. The cutter die structure includes a die carrier 165 and the cutter die 157 fixed to the inner face of the die carrier. The cutter die structure 162 is guided for radial horizontal movement by means of the base 143, the side members 160 and a top member 166 fixed to the side members 160 and the outer member 161.

A cam member 167 is received between the outer member 161 and the die carrier 165 and is guided for vertical movement by means of L-shaped guides 170 fixed to the outer member 161. The cam member 167 has a T-shaped key 171 fixed to its cam face 172 and received within a 7 T-shaped groove 175 in the cam face 176 of the die carrier 165. A fluid motor 177 is fixed to the base 143 of each cutter assembly 140 and has its piston rod 180 fixed to the cam member 167. It can be seen that retraction and projection of the piston rod 180 will move the cam member 167 vertically in opposite directions and will move the die carrier 165 radially inwardly and outwardly.

A latch element 181 is pivoted at 182 to the top member 166 of each cutter assembly 140 and includes a pair of arms 185, each of which has an indentation 186 receivable upon a pair of pins. 187 which extend oppositely from each of the anvil structures 146. The latch element 181 may be swung into and out of engagement with the pins 187 by means of fluid motors 190 each of which are pivoted at one, end to the respective top members 166 and have their piston rods 191 pivoted to the latch elements 181.

Each of the cutter assemblies 140 has an inwardly projecting work piece support 192 fixed thereto. Each anvil die carrier 147 has a pair of bores 200 within which are mounted pin guides 201 which slidably receive guide pins 202 fixed to the die carriers 165. The pins 202 and guides 261 insure that the dies 156 and 157 are maintained centered during the splitting operation.

After the work piece has been dropped into the splitter apparatus and rests upon the work piece supports 192, the latching elements 181 may be swung into engagement with the pins 187, thus locking the upper ends of each anvil structure 146 against horizontal movement with respect to respective top members 166. Thus, the latching elements 181 function to retain the anvil structures rigidly in position so that the cutter dies 157 have a firm back-up member against which to cut. After the latching elements 181 have been properly secured to the pins 187 and the anvils 147 are moved outwardly to properly position the work piece, the fluid motor 177 may be operated to move the cam 167 of each cutter assembly downwardly to cut the scrap areas 79 and to separate the expanded parts 75-78 making up the work piece 158. Preferably, the cutter dies 157 and anvil dies 156 are each formed so that a pair of notches is produced in each scrap portion 79, these notches. assisting in positioning the separated parts in their respective trim die apparatus.

After the parts have been thus separated, the cams 167 are raised by actuation of the fluid motors 177 and each of the cutter dies 157 is retracted outwardly away from the work piece. The separated parts are then free to be conveyed away upon the conveyors 120. The anvil structures 146 are then moved inwardly by fluid motors 142 in readiness for a further work piece by actuation of the fluid motors 142.

From the above description, it will be evident that the present invention provides an improved process and apparatus for forming metallic sheet into parts such as automobile fenders, doors, bonnets and other sheet metal parts. It will also be clear that the present invention provides improved method and apparatus whereby scrap is reduced. At least one reason for this desirable result is that the scrap areas 79 as well as the parts 75-78 are expanded and metal from the scrap areas flows into the parts during the expansion process.

It has also been found that by the expansion step of the present invention, the structural strength of the final part is increased and lighter gauge metal can be used in the parts. Because of the multiple parts formed by each expansion of the closed work piece, speed of production and storage procedure are greatly improved as compared to toggle press operation wherein each stamping produces only a single part. It has also been found that the present invention permits precise forming of parts such as automobile doors and fenders and that this. preciseness greatly exceeds anything known in conventional toggle press procedure, eliminates guesswork and permits formation of parts to very narrow tolerances.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

As used in the following claims, the terms tubular and closed shape are intended to mean cylindrical and also to describe the rectangular shape of FIG. 2 as well as other such shapes.

The invention claimed is:

1. A method of forming sheet metal parts which comprises placing an annular member formed of sheet metal about an inner die structure and within an outer die structure, expanding the inner die structure to stretch the annular member and to force it against the outer die structure to produce a plurality of expanded parts connected by expanded scrap metal, and cutting the scrap metal to separate said parts.

2. A method of forming sheet metal parts which comprises bending a sheet of metal into an annular shape with opposite edges thereof in engagement, welding said opposite edges together, preforming said annular shape to the shape of an unexpanded inner die structure, placing said annular shape about the inner die structure and within an outer die structure, expanding the inner die structure to stretch the annular shape and to force it against the outer die structure to produce a plurality of expanded parts connected by expanded scrap metal, and cutting the scrap metal to separate the parts.

3. A method of forming sheet metal parts comprising forming a sheet of metal into a closed shape with the oppostie edges thereof in engagement, securing the opposite edges together, expanding and stretching the closed shape over a die structure having a discontinuous forming face wherein each continuous portion of said forming face defines one complete surface of a respective one of said parts, and separating the thus formed parts.

4. A method of forming sheet metal parts comprising forming a tubular sheet metal shape, moving a plurality of dies against the inside of said tubular shape from a retracted position wherein the dies are adjacent one another to an expanded position wherein the dies are spaced from one another whereby first portions of said tubular shape are stretched over said dies and second portions of said shape are stretched at the spaces between said dies, and separating said first portions from one another by cutting through said second portions.

5. A method of forming allochiral sheet metal parts comprising forming a tubular sheet metal work piece, moving a plurality of allochirally faced dies against the inside of said tubular work piece from a retracted position wherein the dies are adjacent one another to an expanded position wherein the dies are spaced from one another whereby the tubular work piece is stretched over said dies and the die faces form the work piece into allochiral parts connected by scrap metal, and separating said allochiral parts by cutting through said scrap metal.

6. A method of forming sheet metal parts which comprises placing an annular member having a pair of opposite edges and formed of sheet metal about an inner die structure and within an outer die structure, expanding the inner die structure to stretch the annular member and to force it against the outer die structure to produce a plurality of expanded parts connected by expanded scrap metal portions which extend completely across said annular member from one edge thereof to the opposite edge thereof, and cutting the scrap metal portions completely across said annular member from one edge thereof to the opposite edge thereof to separate said parts.

7. A method of forming sheet metal parts comprising forming a tubular sheet metal shape having a pair of opposite edges, moving a plurality of dies against the inside of said tubular shape from a retracted position wherein the dies are adjacent one another to an expanded position wherein the dies are spaced from one another whereby first portions of said tubular shape are stretched over said dies and second portions of said shape are stretched at the spaces between said dies, and separating said first portions from one another by cutting through said second portions from one edge of said annular member to the other edge thereof.

References Cited by the Examiner UNITED STATES PATENTS Edwards 153-35 Holt 29-412 Palmer 153-35 Ireland 113-48 Beegle 153-2 Budd 29-412 Temple 83-194 Seelofi? 153-80 10 CHARLES W. LANHAM, Primary Examiner. 

1. A METHOD OF FORMING SHEET METAL, PARTS WHICH COMPRISES PLACING AN ANNULAR MEMBER FORMED OF SHEET METAL ABOUT AN INNER DIE STRUCTURE AND WITHIN AN OUTER DIE STRUCTURE, EXPANDING THE INNER DIE STRUCTURE TO STRETCH THE ANNULAR MEMBER AND TO FORCE IT AGAINST THE OUTER DIE STRUCTURE TO PRODUCE A PLURALITY OF EXPANDED PARTS CONNECTED BY EXPANDED SCRAP METAL, AND CUTTING THE SCRAP METAL TO SEPARATE SAID PARTS. 